怎么为DataGrid中的列通过Converter绑定样式

<Application xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
             x:Class="SilverlightApplication15.App"
             xmlns:app="clr-namespace:SilverlightApplication15">
    <Application.Resources>
        <app:DemoComparableConverter x:Key="ComparableConverter"/>
    </Application.Resources>
</Application>

<UserControl x:Class="SilverlightApplication15.Page1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" 
    d:DesignHeight="300" d:DesignWidth="400" 
    xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk">
    
    <Grid x:Name="LayoutRoot" Background="White">
        <sdk:DataGrid AutoGenerateColumns="False"  Name="dataGrid1" >
            <sdk:DataGrid.Columns>
                <sdk:DataGridTextColumn Binding="{Binding Caption}" Header="Caption" />
                <sdk:DataGridTextColumn Binding="{Binding Value}"  Header="Value"/>
                <sdk:DataGridTemplateColumn    Header="Value">
                    <sdk:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding Value}" VerticalAlignment="Center" 
                                       Style="{Binding Converter={StaticResource ComparableConverter}}" />
                        </DataTemplate>
                    </sdk:DataGridTemplateColumn.CellTemplate>
                </sdk:DataGridTemplateColumn>
            </sdk:DataGrid.Columns>
        </sdk:DataGrid>
    </Grid>
</UserControl>

namespace SilverlightApplication15
{
    public partial class Page1 : UserControl
    {
        public Page1()
        {
            InitializeComponent();

            this.Loaded +=(sender ,e)=>
            {
                this.BindControls();
            };
        }
        void BindControls()
        {
            ObservableCollection<DemoComparableClass> demos = new ObservableCollection<DemoComparableClass>();
            demos.Add( new DemoComparableClass("名称A",101) );
            demos.Add(new DemoComparableClass("名称B", 51));
            demos.Add(new DemoComparableClass("名称C", 201));

            this.dataGrid1.ItemsSource = demos;
        }
    }
}

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
namespace SilverlightApplication15
{
    public enum Results
    {
        Normal , Above , Below
    }
    public class DemoComparableClass
    {
        public string Caption { get; set; }

        public int Value { get; set; }

        public DemoComparableClass(string c , int v)
        {
            this.Caption = c;
            this.Value = v;
        }

        public Results Result
        {
            get
            {
                if (this.Value > 100 && this.Value < 200)
                {
                    return Results.Normal;
                }
                else if (this.Value >= 200)
                {
                    return Results.Above;
                }
                else 
                {
                    return Results.Below;
                }
            }
        }
    }

    public class DemoComparableConverter : System.Windows.Data.IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value is DemoComparableClass)
            {
                DemoComparableClass v = (DemoComparableClass)value;
                if (targetType.Equals(typeof(Style)))
                {
                    Style s = new Style(typeof(TextBlock));
                    switch (v.Result)
                    {
                        case Results.Normal:
                            s.Setters.Add(new Setter(TextBlock.ForegroundProperty , new SolidColorBrush(Colors.Brown)));
                            break;
                        case Results.Above:
                            s.Setters.Add(new Setter(TextBlock.ForegroundProperty , new SolidColorBrush(Colors.Red)));
                            s.Setters.Add(new Setter(TextBlock.FontWeightProperty, FontWeights.Bold ));
                            break;
                        case Results.Below:
                            s.Setters.Add(new Setter(TextBlock.ForegroundProperty , new SolidColorBrush(Colors.Green)));
                            break;
                    }
                    return s;
                }
                else if (targetType.Equals(typeof(Brush)))
                {
                    switch (v.Result)
                    {
                        case Results.Normal:
                            return new SolidColorBrush(Colors.Brown);
                        case Results.Above:
                            return new SolidColorBrush(Colors.Red);
                        case Results.Below:
                            return new SolidColorBrush(Colors.Green);
                    }
                }
            }
            return null;
        }
        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}